Methods of rotational casting particularly applied to the formation of cast articles from synthetic plastic resins are well known. In such methods articles are cast in or on molds by placing powdered plastic resin material on to a mold surface heated to a temperature sufficient to melt the plastic resin. The heated mold is rotated simultaneously about two axes perpendicular to each other. The plastic resin melts on the surfaces of the hot mold and is caused to flow over the entire surface of the mold cavity by rotation of the mold. The final thickness of the casting produced is dependent solely on the amount of material initially introduced into the mold. Rotational casting provides castings, with practically no wastage of raw materials, the molded articles being stress-free and of wide variety of shape and size. Rotational casting may also be applied to certain metals and also to glasses. Hitherto, methods of rotational casting have generally employed apparatus wherein the mold is caused to rotate about two axes permanently in a vertical and a horizontal plane respectively, and the rotational speed about each axis is kept constant throughout if uniformity in the casting wall thickness is required (see, for example, U.S. Pat. No. 3,275,733). It has nevertheless been found that with such methods the wall thickness and the internal surface finish of the castings is subject to considerable and uncontrollable unevenness. Moreover, such methods do not lend themselves easily to the production of quality castings from materials introduced into the molds as liquids, e.g. polymerizable plastics, prepolymers, resin monomers etc., as distortion of the cast and gross variations in wall thickness occur.
A method has now been developed which substantially overcomes the aforesaid disadvantages.